Mangiferin is a carbon ketoside of tetrahydroxy pyrrones, as a flavonoid compound of xanthone, existing in a variety of plants, such as mango tree, almond tree, gentiana manchurica and rhizome anemarrhenae, and so on. Mangiferin molecular formula: C19H18O11, molecular weight: 422.3. Mangiferin has many biological activity and pharmacologic actions, such as antioxidation, antitumor, immune regulation, anti-glycosuria and anti-inflammation (Deng Jiagang and Xun Lilan, Journal of Changchun University of Traditional Chinese Medicine, 2008, 24(4): 463-464.).
Although with extensive pharmacologic activity, the dissolvability of mangiferin is very low, and this seriously restricts its development as a medical agent, therefore, to facilitate its use, improvement should be made to the dissolvability and bioavailability of mangiferin. Deng Jiagang et al (Deng Jiagang and Yuan Ye, Western China Pharmacy Journal, 2008, 23 (1):17-18.) converted mangiferin 3-phenolic hydroxyl into a phenol sodium salt, and the mangiferin monosodium salt has a mass yield of 92.8%. Mangiferin converted into sodium salt has improved water dissolvability, and can be easily absorbed in gastrointestinal tract, with improved bioavailability and curative effect; experiments have shown that mangiferin and its sodium salt have the function to relieve cough, reduce phlegm and resist inflammation, with good water dissolvability, the monosodium salt of mangiferin has better action than mangiferin, therefore monosodium salt of mangiferin can be expected to develop into a medicine for respiration system. Hu et al (Hu H G, Wang M J, Zhao Q J. Chin Chem Lett, 2007, 18:1323-1326.) obtained a series of 3,6,7-O-trisubstituted mangiferin derivatives after alkylation with mangiferin as raw material, and their structures were all confirmed by H NMR spectroscopy, with compounds 2˜11 all being new compounds; preliminary in vitro antidiabetic activity sieving result showed that, at the same concentration, the suppression rate of compounds 5 and 11 to PTPIB doubles that of mangiferin.
For natural active ingredients with complicated structure, structural modification with chemical synthesizing has the disadvantages of low yield, poor reaction specificity and many by-products, especially, some reaction can hardly be realized with chemical means at present, but biological transformation can make up the deficiency of chemical synthesizing. Cantagrel et al (Europe Patent File No.: FR20050002223 20050304; Publishing No.: FR 2882762 (A1)) modified mangiferin by glycosylating the mangiferin with glucosyltransferase originated from two strains of leuconostoc mesenteroides, and obtained glucosyl-β-(1,6)-mangiferin, with mangiferin as glycosyl receptor and cane sugar as glycosyl donor (CASRN:908570-23-0). With Leuconostoc mesenteroides NRRL B-1299 strains as biocatalyst, under the condition of 0.4 g/L mangiferin and 40 g/L cane sugar, the yield in glycosylating reaction is 25%; with Leuconostoc mesenteroides NRRL 521-F strains as biocatalyst, under the condition of 0.4 g/L mangiferin and 40 g/L cane sugar, the yield in glycosylating reaction is 28%.
After glycosylation of mangiferin, its water dissolvability is substantially improved, but till today, no relevant research report has been available on whether the change in molecular structure after glycosylating modification will affect the pharmacological activity of mangiferin. Due to the low water dissolvability of mangiferin, in glycosylating modification of mangiferin with biotransformation method, the mangiferin concentration before transformation is generally low (not exceeding 0.5 g/L), and the mole transformation rate of product is also low (not exceeding 30%), and such restrictions have made it quite difficult to obtain sufficient product for pharmacological experiments on tumor-related diseases and the subsequent industrialized production.